1. Field of the Invention
This invention relates to a hot blast type drying apparatus having a deodorizing system combined therewith, for blowing a hot blast against a printed web or sheet for drying the ink thereon.
2. Description of Background Information
In a conventional hot blast type drying apparatus used for a web offset printing press, for instance, for drying a printed portion of a web by evaporizing a solvent in the ink by blowing a hot blast against the web, the hot blast is generated mainly by burning a fuel gas. However, fuel consumption has increased in view of the high speed of the latest high speed printing machines.
In addition, the exhaust gas discharged from a drying apparatus into the atmosphere includes vapors of the solvent from the ink, and the solvent vapor includes bad smelling substances originated from hydrocarbon and ink composition which are the main components of the solvent. Therefore, if the vapors are discharged into the atmosphere and are left intact, complaints may be voiced by neighbors and the atmospheric air may be contaminated.
In order to prevent the above occurrence, there has been hitherto additionally used a burning-up oven called "a deodorizing apparatus". The deodorizing apparatus requiring the least energy consumption is a catalytic type burning-up oven carrying out an oxidizing reaction with the solvent at a comparatively low temperature by using a catalytic layer. This burning-up oven is also such that there is provided a heat exchanger between a duct for discharging the treated exhaust gas from the burning-up oven and a duct for discharging an untreated exhaust gas from the drying oven so that the temperature of the untreated exhaust gas may be raised to some extent and thereafter is preheated by a burner of the burning-up oven to a temperature suitable for the catalytic combustion.
In the above case, it has been usual that the burning-up oven is installed outside a printing room, and the drying oven and the burning-up oven are interconnected by a duct.
The foregoing apparatus has solved, at any rate, an environmental pollution problem, but has raised some problems as mentioned below:
(a) Beside the fuel consumption necessary for the drying oven, an additional fuel consumption for operating the burning-up oven is necessary.
(b) During the time when the used gas is passing through the duct connected between the drying oven and the burning-up oven the gas is cooled and vapors of the solvent contained therein are condensed and adhere to the inner surface of the duct. Further, the vapors may be carbonized or polymerized into high viscous tar during the lapse of a long time period. Such tar is accumulated on the inner surface of the duct. The tar is a combustible substance which may produce a fire in the duct. To prevent this occurrence, the inside of the duct has to be cleaned.
For solving the above problems, a countermeasure is known wherein the burning-up oven is placed on the drying oven so as to make the length of the duct as short as possible to decrease the above problem concerning the duct. Further, a system is known wherein the components of the hot blast circulating in the drying oven is passed through a heat exchanger connected to the burning-up oven and part of the quantity of heat generated at the burning-up oven is collected in the drying oven.
However, even by using the above countermeasures under the best conditions, wherein the amount of ink applied onto the printed web is the largest and the feeding speed of the printed web is the highest, the result is that the amount of calories generated by the total fuel consumption necessary for the drying oven and the burning-up oven can be compensated with the amount of calories generated by the fuel consumption necessary for the conventional hot blast drying oven alone.